The present invention relates to a focal plane shutter for a camera, wherein a set of opening shutter blades and a set of closing shutter blades are operable to open and close a shutter opening.
Conventional camera shutters include a focal plane shutter arranged in front of a film loaded in a camera. There has recently been a need for a lightweight, compact camera. To meet this need, such a conventional focal plane shutter includes a set of superposed opening shutter blades, and a set of superposed closing shutter blades. The opening shutter blades are operable to open a shutter opening. When a predetermined time has passed, the closing shutter blades are operable to close the shutter opening. The opening shutter blades and the closing shutter blades thus cooperate to obtain the proper exposure.
Such a focal plane shutter is illustrated, for example, in FIGS. 2 and 3. In FIGS. 2 and 3, the reference numeral 101 is a cover plate attached to a base plate 102. A set of opening shutter blades 103 and a set of closing shutter blades 104 are assembled between the base plate 102 and the cover plate 101. These sets of opening shutter blades and closing shutter blades 103 and 104 are composed of a plurality of shutter blades which are connected to one end of driving arms 105 and 106 and auxiliary arms 107 and 108. The other end of the driving arms 105 and 106 and the auxiliary arms 107 and 108 are pivotally mounted to the base plate 102.
With the prior art focal plane shutter, a first shutter blade 103a of the opening shutter blades 103 and a first shutter blade 104a of the closing shutter blades 104, one side of which define a shutter opening, are mounted so as not to interfere with pivotal pins 115 and 116 by which second shutter blades are pivotally connected to links. However, this arrangement limits reduction of a space (length L in FIG. 2) defined leftwardly of the shutter opening 120 in the cover plate 101 and thus, limits the size of reduction of the overall unit.
In order to overcome the foregoing problem, there was proposed a focal plane shutter as shown in Japanese utility model publication No. 57367/82. In such a shutter, however, the second shutter blades are supported by elements which are attached to parallel arms. This prevents smooth operation of the shutter and makes it difficult to fabricate the same.
Again, in the prior art focal plane shutter shown in FIG. 2, if the pivotal pins 115 and 116 are mounted closer to adjacent pivot pins 117 and 118 so as to reduce the length L or the space, then the first shutter blades 103a and 104a may not be moved in parallel as they should be. This may adversely affect the configuration of the shutter opening and consequent exposure operation.